Control systems and methods for virtual power plants

ABSTRACT

Systems and methods for the control of distributed systems are presented, particularly virtual power plants. Control software therefore communicates through an interface with decentralized devices. Modules are provided to formulate strategies based on predicted demand for the system, for controlling individual system devices, for system evaluation, for accounting purposes and to provide a user interface.

BACKGROUND OF THE INVENTION

The present invention relates generally to the field of virtual powerplants, but may be broadly applied to distributed systems of devices, orsystems that generate a collective quantity through diverse generatorsto meet a certain demand. Embodiments of the invention relatespecifically to methods and systems for controlling and managing virtualpower plants.

Virtual power plants produce power with high efficiency and are thuslikely to be an important energy source in the future. A virtual powerplant generator network comprises a collection of small, decentralizedpower generating units. These might be, for example, windmills,photovoltaic generators, heat exchangers, fuel cells or fossil fuelgenerators. These generating units are principally located on private,residential properties or public buildings, but can also be present inindustrial or agricultural installations, e.g. by using the heatgenerated by production processes.

The decentralized power generating units may be linked together over acommunications network and controlled using software.

SUMMARY OF THE INVENTION

A first embodiment relates to a distributed system control unit,comprising at least one communications interface; the at least onecommunications interface coupled at least indirectly to two modules;wherein a first of the two modules comprises executable code forcontrolling at least two geographically distributed devices; and whereina second of the two modules comprises executable code for developing astrategy to control the at least two geographically distributed devices.

A second embodiment relates to a method for controlling a plurality ofgeographically distributed devices, comprising the steps of: receivingdata comprising active status and output of at least one device througha communications interface; calculating a system state; calculating,based on the system state and historical data a predicted demand; andcontrolling through the communications interface the at least one devicecorresponding to the predicted demand.

A further embodiment relates to a machine readable medium havingcomputer code embedded therein which, when executed causes the machineto perform a method comprising the steps of: receiving data from aplurality of power generating devices, the data indicating an activestate and, if active, an output of each device; receiving historicaldata from a database; calculating a predicted power demand; andcontrolling each of the plurality of devices to change a system state ifthe predicted demand is different than a present system state.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a representative virtual power plant.

FIG. 2 is a block diagram depicting elements of an exemplary controlsystem for a virtual power plant.

FIG. 3 is a block diagram of modules exhibiting standard interfacecommunications.

FIG. 4 shows the integrations of modules into a control system for avirtual power plant.

FIG. 5 shows the organization of one embodiment of a control system fora virtual power plant.

FIG. 6 is a flow diagram describing the function of an Energy Demandmodule.

FIG. 7 is a flow diagram describing the function of a Control of PowerGenerators module.

FIG. 8 is a flow diagram describing the function of a Graphical Displaymodule.

FIG. 9 is a flow diagram describing the function of an Accountingmodule.

FIG. 10 is a flow diagram describing the function of an Evaluationmodule.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

While the following description will primarily relate to virtual powerplants, embodiments of the present invention are envisioned as beinguseful in a number of applications involving the control of devicesspread over a wide geographical area, but used for a common purpose.

A representative virtual power plant 100 is shown in FIG. 1. The virtualpower plant 100 has a control unit 102, utility grid sections 104, 106and 108, solar power generating units 110, 112 and 114, fuel cellgenerators 116, 118 and 120, and fossil fuel generators 122 and 124. Itshould be understood that the choice of generating units is merely forthe sake of example. The generators 110 through 124 are generallygeographically distributed. Also shown are communications networks 126,128 and 130.

Each geographically distinct generating unit 110 through 124 isconnected to a utility grid connection point. This allows the generatingunits to produce power that can be supplied to the grid to which it isconnected. Each power generator 110 through 124 also has an isolationcircuit (not shown) that allows the generator to be decoupled andisolated from the grid should it be desirable to take the generatoroffline. It should be noted that utility grid sections 104, 106 and 108may be part of the same grid, which can be a public or private network.

Each geographically distinct generating unit 110 through 124 is alsoequipped with a communications interface (not shown) that allows it tocommunicate with control system 102 through one of networks 126, 128 or130. Communication may be had over any readily available link, includingpublic IP networks, but is preferably performed over a private,encrypted network for system security. The generators 110 through 124may be redundantly coupled to multiple networks to control system 102.

Control system 102 uses communication networks 126, 128, and 130, whichmay be the same network, to control the operation of the virtual powerplant 100. Each of the power generators 110 through 124 reportsinformation regarding its current status, for example, the current powerlevel it is producing for the network, its current maintenance status,available fuel supply, if applicable, local loads, etc. The controlsystem 102 accepts and processes incoming information about generators110 through 124 and makes predictions about future energy demand, andmakes corresponding changes to the generating status of power generators110 through 124 based on the predicted demand.

One embodiment of a control system may be seen in reference to FIG. 2,which is a block diagram of a control system for a virtual power plant,such as the power plant 100 shown in FIG. 1. Control system 200 shouldbe understood as software such as that employed by SAP AG, running on ahardware platform suitable for the computational task. Control system200 has a communications interface 202, communications connections 204,and control software 206, which further comprises modules 208, 210, 212,214 and 216. Control software 206 further comprises a data storage andretrieval mechanism 218.

The control software 206 is able to control virtual power plants and toassist in the solution of tasks that occur in the management of suchvirtual power plants. In order to accomplish this, the control programis constructed of highly integrated, modular components 208 through 216.These components comprise the functionality for planning a powergeneration strategy, evaluating the current state of the power plant,controlling individual power generation, accounting for power generationand the attendant costs, revenues and bookkeeping, as well as theprovision of an control system operator interface. The control software206 may include further modules as needed for the management of tasks asthey arise during the course of virtual power plant operation.

In a preferred embodiment, modules forming parts of the control software206 SAP are constructed in a highly integrated and modular fashion. Anexemplary module 300 is shown in FIG. 3. Here, the term “module” shouldbe understood to mean a collection of code to perform one or moreparticular functions. Module 300 comprises a module process, which willbe understood by a person of ordinary skill in the art to be a set ofprocedures and data that carry out the purpose of the module.

Module 300 also comprises interfaces 304 and 306. It should beunderstood that module 300 may have a variety of interfaces depending onthe needs of the system. Interfaces 304 and 306 are preferablyApplication Programming Interfaces (APIs) that allow the passage of datain a standardized way, where standardized means that the interface thatthe interface has components that do not change through differentversions of the control software. The interfaces 304 and 306 are used bymodule 300 and at least one other module (not shown) to exchange datathrough communication pathways 308 and 310. A suitable interface is anyinterface that allows a second module to communicate with module 300without the second module having direct access to the data space ofmodule 300 in the module process 302.

Preferably, the interfaces also provide an encapsulation that allows thecorresponding modules to communicate over suitable standardizedinterfaces with programs and applications from third party providers.The Modules can also be integrated into programs and applications fromthird parties. The reverse is also true: more technically orientedprograms from third party providers can be integrated into the controlsoftware over suitable standardized interfaces. The control software isthus capable of providing the functionality of the central controlprogram of a virtual power plant.

The modularity is illustrated in FIG. 4, wherein a control system isdescribed in reference to a specific embodiment. Control system 400 hasa communications interface 402 and communications connections 404,similar to the control system shown in FIG. 2. Control system 400 alsohas control software 406, which comprises a generator control module418, a planning module 410, an accounting module 412, an evaluationmodule 414 and a control system user interface module 416. Each module410 through 418 also has at least one corresponding interface 420, 422,424, 426, and 428, through which the modules communicate with oneanother. Generator control module 418 is further in communication withindividual, decentralized generators through communications interface402. Generator control module 418, in this embodiment, can thus providestate information relating to the decentralized power generators toother modules as needed, and can control the decentralized modules bysending signals to the decentralized power generators that comprisecontrol signals or command information.

Control system 400 also comprises an information storage subsystem 430such as those known in the art, which is responsible for keeping trackof the system state, historical data, accounting data, and variousinformation used to perform calculations in each of the modules.Subsystem 430 may comprise a number of databases and correspondinginterfaces or managers that allow access to information from the varioussystem modules.

A further embodiment of the control system is depicted in FIG. 5. FIG. 5shows a control system 500 having a communications interface 502,communications connections 504, and a control software 506. Controlsystem 500 also comprises a module 508 for integration of other systemmodules; a module 510 for planning of the expected energy demand; amodule 512 for communication of the individual power generators with thecentral control and for control of the individual energy producers inreal time; interface modules 514, 516 and 518 for interfacing with thirdparty modules and systems; a module 520 for the calculation of thecosts/contributions of power for the individual power generators(accounting); a module 522 for performing system evaluation andcomputation of the system state; and a module 524 for the visualization(via a user interface) of planning, control and accounting data.Subsystem 526 is responsible for data storage and management, much assubsystem 430 in FIG. 4.

Module 508 acts as a data switch to communications interface 502 andprovides other modules with interfacing for intermodule communications.Of course, it should be noted that the arrangement of FIG. 4 may also beused, or some combination of the two. That is, some modules may be indirect communication with each other or communications interface 502through their own integrated interfaces, while other modules maycommunicate through systems integration module 508. Module 508 alsoperforms housekeeping activities such as records storage and maintenanceby means of subsystem 526.

Modules 514, 516 and 518 provide standardized interface functionalityfor third party or additional modules that may be used depending on userpreferences. For example, it may be necessary or advisable to generatereports specific to a third party user format, or it may be necessary oradvisable to communicate with a third party database or foreign system.Interface modules 514, 516 and 518 provide flexibility throughstandardized interfaces for performing integration to foreign systems.

Modules 510 and 512, in combination with module 522 provide thecomputational engine of the control aspects of the system. It should benoted that these modules may be integrated into a single module, butthat advantages can be achieved when divided. This is particularly truein the case of virtual power plant systems, where a wide variety ofsystems comprising decentralized power generators may need to beintegrated and controlled in the system. It is therefore also to be seenthat advantages can be obtained by further modularity. This can mean,for example, dividing control module 512 into a number of submodules,each specific to a particular generator type (including manufacturer,model number, communications interface, etc.). Modules 510, 512 and 522provide a number of services for managing virtual power plants,including automatic reaction to disturbances and failure ofdecentralized power generators (intelligent and independentcompensation).

A data flow chart for an exemplary planning module is explained hereinwith reference to FIG. 6. Information (status, current power, load,etc.) from the individual, decentralized power generators connected tothe network is delivered (602) to the information interface 606 of theexemplary planning module. This information may be delivered from anyrelevant pathway but is preferably delivered from a system evaluationmodule over a corresponding interface.

The planning module also has access to stored historical information,which can be provided, for example, by database manager 614 toinformation interface 606. It should be understood that any conventionalstorage scheme may be used. Information provided by database manager 618may relate to previous states of the system, including load, energydemand and individual generator status/performance information. It mayalso including historical load/demand information correlated to thetime, as well as other pertinent information (such as current weatherconditions). The information is pre-processed at 608 and passed tointelligent prediction algorithms 610, which are responsible for futureenergy demand as well as updating prior predictions with more currentdata. In addition, the information is passed to a strategy output 612which transmits information to database manager 614. Database manager614 transmits data 604 to information interface 606.

The planning module thereupon generates strategies that guide thecovering of short, mid and long-term energy demand. Strategies take intoaccount a number of factors, including the availability of individual,decentralized power generators, cost/power functions known or estimatedfor individual power generators, the availability of stored energy andits cost, the projected load and demand volatility, as well as economicfactors such as incentives that may be affected through use ofparticular generators. The Planning module attempts to develop astrategy that will optimize cost performance while still maintaininghigh reliability. The results of the strategy are fed back for storageto database manager 614 and output (616) to generator control module 618over an appropriate interface.

An exemplary generator control module is now delineated in greaterdetail in reference to FIG. 7. The generator control module receivesdata (702) from the planning module through a corresponding interface.This information is communicated to decision section 706, which may alsouse information from a system evaluation module 708. Decision section706 implements the strategies of the planning section by controllingindividual, decentralized power generators through the control interface712 via a generator control 710. Information about control decisionsmade is output to other system elements 714 responsible for keepingtrack of the system state.

The control module has several options for control. According to thecircumstances, generators can be taken on or offline, or their outputredirected to storage if available. If an active decentralized powergenerator suddenly goes offline, the generator control module hasseveral possibilities to compensate for the gap in production:increasing the energy production of online decentralized powergenerators; taking addition power generators online or switching energystorage units online. Moreover, based on a comparison between planneddata and actual data, additional activities can be carried out, if forexample the power of a generator lies outside of its specific range,which can indicate a problem. Here the generator control module cancause the execution of diagnostic and repair programs or send messagesand reports to the repair team.

An exemplary control system user interface is described with referenceto FIG. 8. The control system user interface module receives input (802)from the user through a user input interface 804. Input interface 804may be in communication with a display constructor 806. Displayconstructor 806 may be in communication with a user output 810. Thisinformation allows the module to understand how the user wishes toconfigure control system user interface output. Information about thecurrent system state and predicted state data is also communicated (808)to the module.

The display constructor 810 has the capability to display data from thecontrol system as well as data from integrated programs and applicationsfrom third parties in a form suitable for users over output 812. Thedisplay format is evaluated interactively dependent on the applicationcontext. For example, the overview of periodic data concerning plannedand actual power generation can be prepared and displayed as a table.The detailed data for a decentralized power generator, such as forexample the power level, can be visualized as power curves. The overviewof status (active, inactive, out of order, etc.) of the decentralizedpower generators of a virtual power plant are displayed with suitablepicture elements (LEDs, stoplights, etc.) All indicators generated bythe display constructor are automatically updated when the underlyingdata changes through the input of state information 808. The user hasthe opportunity to change the graphical display according to suit his orher needs.

An exemplary accounting module is described herein with reference toFIG. 9. The accounting module receives information about past states(902) through an information interface 904, as well as storedinformation necessary to perform financial calculations, such as tariffplans and information that may be supplied by third parties, such ascurrent rate structures. This information is used by a calculationsection 906 to generate reportable data in calculation section 906,which is past to report generator 910. Report generator 910 generates,based on the data for the decentralized power plants, correspondingreports. The reporting flow over electronic communication with theaccounting entities 912 of the power plant operators and operators ofdecentralized power generators is supported as is the printing ofreports on paper. Through an exchange of data with authorities, thefocused and automatic implementation of tax-based withholding orincentive programs can be carried out. Accounting data is also passed torecord-keeping 914 for proper archival of the information. In anexemplary embodiment, a database manager 908 may be in communicationwith an external source 916 and calculation section 906.

An evaluation module is explained with reference to FIG. 10. Theevaluation module comprises analytical and calculation programs to aidethe investigation and evaluation of current data from the virtual powerplant network. It receives over an appropriate information interface1002 both stored information from a database manager 1004 or othersuitable storage system as well as information about current devicestate through a generator interface 1006. Evaluation section 1008computes a standardized set of system state data and may check this dataagainst criterion indicative of system health provided by databasemanager 1004. Evaluation section 1008 may be in communication with anoutput generator 1010. Output Generator 1010 may be in communicationwith a generator control module 1012. Together with the rest of thecontrol system modules, this allows simplified maintenance of thevirtual power plant as well as proactivity (on the basis of predicteddata).

While the invention has been described with reference to variousembodiments, it will be understood by the person of ordinary skill inthe art that such embodiments are exemplary of the invention, and do notdefine it in a restrictive manner.

1. A distributed generation system, comprising: a first power generationunit, the first power generation unit comprising a first controlinterface, the first control interface configured to control a powergeneration of the first power generation unit, the first powergeneration unit being a structure able to generate power; a second powergeneration unit, the second power generation unit comprising a secondcontrol interface, the second control interface configure to control apower generation of the second power generation unit, the second powergeneration unit being another structure able to generate power; acentral controller comprising a strategy module and a control module,the central controller is configured to communicate a first controlcommand to the first control interface and to communicate a secondcontrol command to the second control interface; and the strategy moduleis configure to determine a first power output of the first powergeneration unit and a second power output of the second power generationunit based on a tariff structure, a first unit capacity, a second unitcapacity, a first unit availability and a second unit availability, thefirst power output of the first power generation unit being a firsttargeted power production level of the first power generation unit andthe second power output of the second power generation unit being asecond targeted power production level of the second power generationunit, the first unit availability being based on whether the first powergeneration unit may be utilized to produce power and the second unitavailability being based on whether the second power generation unit maybe utilized to produce power; wherein the first control command is basedon the first power output of the first power generation unit; whereinthe second control command is based on the second power output of thesecond power generation unit.
 2. The distributed generation system ofclaim 1, wherein the strategy module is further configured to determinethe first power output of the first power generation unit and the secondpower output of the second power generation unit based on a first costof the first power generation unit and a second cost of the second powergeneration unit.
 3. The distributed generation system of claim 1,wherein the strategy module is further configured to determine the firstpower output of the first power generation unit and the second poweroutput of the second power generation unit based on a projected load anda demand volatility.
 4. The distributed generation system of claim 1,further comprising a third module, comprising executable code forevaluating a current state of each of the first power generation unitand the second power generation unit.
 5. The distributed generationsystem of claim 1, wherein the strategy module is further configured todetermine the first power output of the first power generation unit andthe second power output of the second power generation unit based on aprojected load and a demand volatility and wherein the projected loadand the demand volatility are based on a weather condition.
 6. Thedistributed generation system of claim 1, wherein the strategy module isfurther configured to determine the first power output of the firstpower generation unit and the second power output of the second powergeneration unit based on a first power generation unit performance and asecond power generation unit performance.
 7. The distributed generationsystem of claim 1, further comprising a fourth module, comprisingexecutable code for accepting system state data and generating thereupona report of costs and revenue.
 8. The distributed generation system ofclaim 1, wherein the strategy module is further configured to determinethe first power output of the first power generation unit and the secondpower output of the second power generation unit based on a first costof the first power generation unit, a second cost of the second powergeneration unit, a projected load, a demand volatility a first powergeneration unit performance, and a second power generation unitperformance.
 9. The distributed generation system of claim 8, furthercomprising a third module, comprising executable code for evaluating acurrent state of each of the first power generation unit and the secondpower generation unit.
 10. The distributed generation system of claim 9,further comprising a fourth module, comprising executable code foraccepting system state data and generating thereupon a report of costsand revenue.
 11. The distributed generation system of claim 1, wherein afifth module comprises executable code for receiving data relating to acost performance function of at least one of the first power generationunit and the second power generation unit.
 12. A method for controllinga plurality of geographically distributed devices, comprising the stepsof: receiving a first status of a first power generation unit and afirst output of the first power generation unit, the first powergeneration unit being a structure able to generate power, a first poweroutput of the first power generation unit being a first targeted powerproduction level of the first power generation unit; receiving a secondstatus of a second power generation unit and a second output of thesecond power generation unit, the second power generation unit beinganother structure able to generate power, a second power output of thesecond power generation unit being a second targeted power productionlevel of the second power generation unit; calculating a system statebased on the first status, the second status, the first output and thesecond output; calculating, based on the system state and historicaldata, a predicted demand; determining a third output of the first powergeneration unit based on a tariff structure, a first unit capacity, anda second unit capacity; determining a fourth output of the second powergeneration unit based on the tariff structure, the first unit capacity,and the second unit capacity; controlling through a communicationsinterface at least one of the first power generation unit and the secondpower generation unit based on at least one of the third output and thefourth output; and storing data relating to the first output, the secondoutput, the third output, and the fourth output.
 13. The method of claim12, wherein the third output of the first power generation unit isfurther based on a first cost of the first power generation unit. 14.The method of claim 12, further comprising calculating based on cost toperformance data a strategy based on the predicted demand.
 15. Themethod of claim 14, wherein the strategy comprises data indicating afuture active status of the first power generation unit and the secondpower generation unit.
 16. The method of claim 12, further comprisingthe step of generating a report based on the system state.
 17. Themethod of claim 12, wherein the step of controlling through thecommunications interface the at least one of the first power generationunit and the second power generation unit based on the at least one ofthe third output and the fourth output comprises controlling the firstpower generation unit and the second power generation unit through aninterface specific to the first power generation unit and the secondpower generation unit.